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Mark 1948 Guest
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Posted: Tue Nov 28, 2006 9:26 am Post subject: Toshiba 21N21B2 PSU fails once a week. |
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I have a Toshiba here (TMC572B Chasis) that keeps knocking out the Line Output transistor a 2SD2499. The PSU then trips for a few seconds and pops the FET 2SK2499 and various other compnents. The PSU type is SOPS
It popped for the 3rd time this morning and I am at a loss, I have rebuilt it again and it runs fine but have turned it off as I am clearly missing something.
What has been done:
1) Changes the Line Output transistor 2SD2499 and block soldered for dry joints
2) The PSU needed 2SK2651, 0.22 Ohm 1W feed resistor, 18v Zenor. I have changed the 1.2 Ohm resistor between Source and ground even tho it measured OK.
The failure of the Line Output transistor could be down to a cap or something else but when it fails the PSU should trip not got pop????
Oh and the HT is at 125v which for a 21" seems about right. |
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minnie
Joined: 18 Aug 2005 Posts: 2881 Location: Hell
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Posted: Wed Nov 29, 2006 1:20 am Post subject: |
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If the line out put transistor is the horizontal out put transistor off the flyback I'd say change the flyback/trippler/doubler. I call it a flyback. The transformer that has the red lead that goes to the picture tube. |
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